Real Estate
The sprawling green rooftop on the Brooklyn Grange at the Brooklyn Navy Yard.
Dig this before installing a green roof
BY LIZ SADLER CRYAN
It’s hard to miss the soaring 3-acre
meadow that graces the top of Barclays
Center in Downtown Brooklyn.
But green roofs — or living roofs,
as they are also known — are also
branching into residential neighborhoods,
where homeowners with sturdy
enough roofs can enjoy their environmental
and fi nancial benefi ts.
“Not only are green roofs really beautiful,
nice places to hang out and good
for the environment, but they save the
building on energy costs and make it a
lot cooler,” said Inger Yancey of Brooklyn
Green Roof. “The top fl oor will be
5 to 7 degrees cooler than outside, if it
has a green roof. It also cuts down on
sound, and in winter it keeps more of
the heat inside.”
Green roofs can also extend the life
of a roof by 50 years or more by adding
a layer of protection from the sun and
other elements.
If you’re considering a green roof on
your brownstone rooftop, here’s what
you need to know:
“The place to start is with the structural
integrity of the roof,” said Eric
Dalski of Highview Creations.
A structural engineer can provide an
assessment by reviewing architectural
drawings or drilling into the ceiling to
see the joists.
“What is a problem is when the
weight is too much and you can have
cracking,” Dalski said. “I recommend
a leak-detection test or new roof that
is certifi ed by a roofer, so it’s good to
go.”
Though steel joists are preferable
to support the weight of a green roof,
most brownstones and row houses have
wood ceiling beams.
“But the narrow span means wood
is usually not a problem,” said Gwen
Schantz of Brooklyn Grange. “Most
brownstones you can generally put a
shallow green roof with 4 to 5 inches
of soil. Or you can put in a smaller
green roof, too, and just cover part of
the roof.”
The design of the green roof will
depend on the strength of the roof: A
stronger roof will allow for deeper soil
and more diverse plantings, such as
wildfl owers and vegetables.
“For rooftops that can’t hold a lot
of weight, we put in plantings called
sedum that do a good job of capturing
storm water and are also low maintenance,”
Dalski said. “If the roof allows
it, we love to make a deeper soil profi le
and throw in native plantings — what
we see in fi elds and forests, pollinators
that will attract birds and bees.”
Yancey often uses a combination of
sedum and perennials.
“Sedum never needs to be replanted,”
she said. “It goes dormant in winter,
is drought-tolerant and low- maintenance,
and doesn’t need to be pruned
or mowed. I typically use sedum as a
kind of a base because it’s so resilient.
And I use native perennial plants because,
as an environmentalist, I want
to be creating a kind of ecosystem up
there that’s going to be useful to the
birds and bees and butterfl ies that are
going to populate it.”
Installation can take less than a
week or up to a month, depending on
the scope of the project. The fi rst step
is usually to lay down a coat of heavy
plastic or rubberlike material to keep
the roots from penetrating the roof and
to separate the green roof from the roof
membrane. That is then covered by a
drainage layer or mat. A layer of fabric
is often used beneath the soil to prevent
it from seeping into the drainage.
An irrigation system is usually recommended
for the hottest months.
“One thing that’s really important in
designing a green roof is making sure
you’re placing the plants in a way that
is not going to encourage leaks,” Yancey
said. “You want to make sure roots
can’t reach any portion of the roof
PHOTO BY SUSAN DE VRIES
where water might collect. On a roof,
it would be where vertical meets horizontal
— a skylight, cornice, parapet
or vent — and it’s likely to crack over
time. Anyplace that there’s a crack is a
place where, if the crack is worsened,
water can start coming in.”
Prices start at $25 to $35 per square
foot for a basic green roof, and $35 and
up for a more elaborate system. A city
tax-abatement program for green roofs
expired last year, but is likely to be renewed.
Green roofs don’t typically need to
be watered because the plantings are
drought-tolerant. But they do require
some maintenance, such as weeding
and trimming back at the end of the
season.
“I think green roofs are just kind
of coming onto the scene right now,”
Yancey said. “It seems like a new technology,
and an exciting new architectural
element that you can add to your
building. But the reality is they’re not
very different from good old-fashioned
planter boxes. They’re just a little more
intelligently engineered.”
This article fi rst ran in Brownstoner,
a sister Schneps Media publication of
The Villager.
26 September 12, 2019 TVG Schneps Media